We need to find solutions how to stop scammers, hackers and criminals
But the sad reality is that we cannot stop scammers, criminals as you have said above. Generally there are hackers in the internet and hackers have been in existence before they advent of cryptocurrency. But the existence of cryptocurrency has aided the job of hackers such that it does not appear difficult again for them to hide the funds when they succeed to steal it. Cryptocurrency is characterized by scam, the best we can do is to learn how not to fall victim to scams. But stopping scam is something that is unachievable, no matter the level of security and enacted laws.
These scammers are most times smarter than their victims because they are innovative, looking for new ways to scam. What we really need to do is to learn how to counter their strategies as they invent them.